The last decade has witnessed a fundamental paradigm shift on how information content is distributed among people. Traditionally, the majority of information content has been produced by few specialized agents and consumed by the big masses. Nowadays, an increasing number of platforms allow everyone to participate both in information production and in information consumption. The phenomenon has been referred to as democratization of content. The Internet has had a major role in this paradigm shift. User-generated content and social media have also contributed to the paradigm shift. Blogs, micro-blogs, photo-sharing systems, and question-answering portals, are some of the social media that people participate in as both information suppliers and information consumers. The Internet, as well as social systems, offer significant opportunities for consumers to experience content and for suppliers to have an audience for content.